Development of coating structure and adhesion during high velocity oxygen-fuel spraying of WC-Co powder on a copper substrate

This paper deals with the mathematical modeling of the development of the W C-Co coating structure and adhesion on a copper substrate during high veloc ity oxygen-fuel (HVOF) spraying. Two types of substrates are considered: sm ooth (polished) and rough (grit blasted), Variations of solidification time , solidification velocity, thermal gradient, and cooling velocity in the co ating and substrate interfacial region are studied. Development of the amor phous and crystalline structures in the coating and of the crystalline stru cture in the substrate interfacial region is discussed. Behavior of the cry stal size and intercrystalline distance with respect to the thermal spray p arameters and morphology of the substrate surface is analyzed. Optimal cond itions for the formation of fine and dense crystalline structure are determ ined. Structural changes in the solid state of the substrate occurring beca use of heating and rapid cooling are considered. Mechanical and thermal mec hanisms of development of the substrate-coating adhesion are discussed, Res ults obtained agree well with experimental data.